1Department of Urology, The First Affiliated Hospital of Anhui Medical University and Institute of Urology, Anhui Medical University, Hefei, Anhui 230022, China2School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230027, China

Received 29 March 2014; Revised 22 May 2014; Accepted 18 June 2014; Published 6 July 2014